1. Field of the Invention
The present invention relates to a rubber contact switch used in an automobile or the like and, more particularly, to a rubber contact sheet formed on a printed board.
2. Prior Art
A conventional rubber contact switch is disclosed in Japanese Unexamined Utility Model Publication No. 6-3752. A rubber contact switch shown in FIG. 1 in this publication comprises a rubber contact sheet consisting of a silicone rubber, a pair of pressing members are vertically movably arranged on the rubber contact sheet. The upper end of each pressing member is in contact with a key top. The key top is horizontally oscillated to turn on/off a switch of the printed board. The left pressing member consists of a transparent member such as polycarbonate or acrylic. Light rays from a chip-type LED mounted on the printed board are transmitted to the pressing member through the transparent rubber contact sheet to illuminate the illumination point of the key top.
FIG. 3 in this publication shows an arrangement in which an LED with a lead line is used in place of the chip-type LED, and this LED is arranged between the pressing members. In this rubber contact switch, the lead line of the LED extends to the rear side of the printed board through a hole formed in the rubber contact sheet, and the end portion of the lead line is soldered on the rear surface of the printed board.
In the former rubber contact switch, the chip-type LED is directly mounted on the printed board to keep water resistance and dust resistance. In this arrangement, when brightness control is to be performed, the position of the LED or the shape of the rubber contact sheet must be changed. For this reason, a large change in design must be performed to achieve the brightness control.
In the later rubber contact switch, the LED with a lead line is used, and brightness can be controlled by a height at which the LED is mounted. For this reason, the former drawback can be removed, but the following problem is posed.
More specifically, when the end portion of the lead line is soldered on the rear surface of the printed board, heat is transmitted to the rubber contact sheet, a portion, where the rubber contact sheet is in contact with the lead line, near the soldered portion may be disadvantageously melted, deformed, or deteriorated.